Visualization of Droplet Nucleation on Patterned Hybrid Surfaces

Abstract

Abstract Hydrophobic-hydrophilic hybrid surfaces have the potential to enhance and optimize condensation heat transfer. The optimum design of hybrid surfaces has been shown to greatly improve heat transfer performance when compared to that of pure hydrophobic or hydrophilic surfaces. However, challenges remain related to the manufacture of hybrid patterns on large area samples. Here, we develop and visualize a simple stamping method to pattern surfaces for well-defined hydrophobic and hydrophilic regions. The reversible control of adhesion of patterned Polydimethylsiloxane (PDMS) stamps was utilized to form arrays of hydrophilic regions on HTMS (Heptadecafluoro-(tetrahydrodecyl) Trimethoxysilane). To visualize the nucleation behavior, we utilized optical microscopy. Water condensation on the hybrid surfaces resulted in nucleation of droplets that initiated on the hydrophilic patterns. The visualizations shown here not only demonstrate the spatial control of heterogeneous nucleation of water, but present design guidelines for the development of scalable hybrid surfaces for the study of controlled droplet nucleation phenomena and to enable the control of droplet distribution and density during dropwise condensation.